Process of preparing mercaptophenols

ABSTRACT

A process is described for preparing polythiobisphenols and for converting these into mercaptophenols. The reaction between a phenol and sulfur as catalyzed by a Friedel-Crafts catalyst is interrupted before completion, and the product, a phenol polysulfide mixture is reduced to mercaptophenol. A continuous process is described wherein by-product phenol monosulfides are converted to a phenol.

United States Patent 1 Geering et a1.

[ 51 Feb. 20, 1973 PROCESS OF PREPARING MERCAPTOPHENOLS [75] Inventors:Emil J. Geering, Grand Island;

George B. Stratton, Lewiston, both of N.Y.

[73] Assignee: Hooker Chemical Corporation,

Niagara Falls,N.Y. [22] Filed: May 21, 1971 [21] App1.No.: 145,960

Related US. Application Data [62] Division of Ser No. 780,100, Dec. 30,1968, abandoned.

[52] US. Cl. ..260/609 D, 260/470, 260/516, 260/608, 260/609 F, 260/621H [51] Int. Cl ..C07c 149/36 {58] Field of Search ..260/608, 609 D [56]0 References Cited I UNITED STATES PATENTS 3,406,158 10/1968 Brown eta1. ..260/l37 FOREIGN PATENTS OR APPLICATIONS 1,045,813 10/1966 GreatBritain ..260/l37 Primary Examiner--Lewis Gotts Assistant Examiner-D. R.Phillips Attorney-Peter F. Casella, Donald C. Studley, Richard P.Mueller and James F. Mudd [5 7] ABSTRACT 14 Claims, No Drawings PROCESSOF PREPARING MERCAPTOPHENOLS This application is a division ofapplication Ser. No. 788,100, filed Dec.30, 1968 now abandoned.

This invention covers a novel process for preparing polythiobisphenolsand for converting these into mercaptophenols. The reaction between aphenol and sulfur as catalyzed by a Friedel-Crafts catalyst isinterrupted before completion and the product, a phenol polysulfidemixture, is reduced to a mercaptophenol. The invention also covers acontinuous process for preparing polythiobisphenols by convertingby-product phenol monosulfides to a phenol by hydrogenolysis.

The base catalyzed reaction between a phenol and the sulfur has beendescribed in co-pending patent application Ser. No. 597,228 filed Nov.28, 1966, now abandoned, and Ser. No. 666,915, filed Sept. 11, 1967, nowUS. Pat. No. 3,468,961, issued Sept. 23, 1969. These applicationsdescribe conditions for conducting the above reaction to give phenolpolysulfides in which the sulfur atoms are attached primarily inpositions ortho to the phenolic hydroxyls.

Less well-known is a phenol sulfur reaction as conducted under acidicconditions. A recent British Pat. No. 1,045,813, discloses sulfurizedphenols formed by heating sulfur and phenol in the presence of aluminumhalides, ferric chloride, zinc chloride and stannous bromide. Theseproducts contain mainly monosulfide bonds. The course of the reaction,as described in this patent, can be followed by observing the evolutionof hydrogen sulfide. The reaction is terminated when this evolutionceases or when the rate has fallen to a very low figure. Under thesecircumstances, most of the sulfur in the sulfurized phenol will bepresent as monosulfide bonds.

Phenol sulfides, i.e., sulfurized phenols, containing more than onesulfur atom per sulfur bond are unsatisfactory for most applicationswhere they must retain their molecular integrity and in which they willbe subjected to heat or to the action of nucleophilic or electrophilicreagents, because of the laible nature of the polysulfide bond. Phenolmonosulfides, unlike phenol polysulfides, are suitable for example, asantioxidants for polymers and as raw materials for epoxy resins. Theseuses are described in the cited British patent.

It has been known to employ sulfur chloride as reactant for theproduction of phenol sulfides in which phenol rings are linked by one ormore sulfur atoms. This, thereby, involves higher manufacturing costs inthe processes of this invention and are accompanied by additionalproblems. For example, when sulfur chloride is the initial reactant itmay be more expensive than the sulfur reactant employed in the processof this invention. Further the condensation of phenol and sulfurmonochloride or sulfur dichloride is accompanied by the formation ofhydrogen chloride as a by-product. A process for preparing phenolsulfides which includes the condensation of phenol and a sulfur chloridemust therefore include steps involving special materials of constructionfor handling the corrosive gas, hydrogen chloride, which is evolvedduring the process.

The prior art process employing sulfur chloride has a disadvantage ofrequiring additionally an extra step, i.e., a sulfur chlorination stepto produce sulfur chlorides as well as a step for disposing of acorrosive by-product gas, HCl. Further, the employment of a sulfurhalide as a reactant, in the reaction with phenol, often results inchlorinated by-products.

A further problem with the sulfur chloride reactant is the formation ofa large yield of phenol monosulfide, which is not directly convertibleto the desired mercaptophenol.

In J. Gen. Chem., 29, 2236-2239 (1959) a yield of about 96 percentbis(trichlorophenyl) trisulfide was obtained by employing elementalsulfuras a reagent along with sulfur chloride and trichlorobenzenecatalyzed by Friedel Crafts compounds. However, this technique does notgive polysulfides in a satisfactory yield when applied to a phenol. Thephenol-sulfur chloride process described in US. Pat. No. 3,275,694 givesphenol polysulfides but requires hydrogen sulfide as a secondsulfur-containing reagent.

From US. Pat. No. 2,937,208 and US. Pat. No. 3,275,694 it is known toemploy Friedel-Crafts catalysts in the reaction of phenol and elementalsulfur. However, these references or other similar references whetherdescribed above or not, do not describe an interruption of the reactionin order to obtain a product which would subsequently give suitably highyields of ortho or para mercaptophenols, preferably ortho.

It is an object of this invention to produce a polysulfide compoundsuitable for reducing to ortho or para mercaptophenol, preferably ortho.

Another object is to obtain improved yields in the process for preparingortho or para mercaptophenols.

It is also an object to continuously produce a polysulfide which can beconverted to a mercaptophenol.

It is a further object of this invention to eliminate the undesirableuse of corrosive substances such as HCl and to employ lowermanufacturing costs in the production of ortho or para mercaptophenols.

The objects of this invention are achieved by heating a phenol andsulfur in the presence of a Friedel-Crafts catalyst until up toone-third of the sulfur has been expelled as hydrogen sulfide. As shownin the following equation, which is a preferred reaction, when one-thirdof the sulfur has been converted to hydrogen sulfide, the average sulfurbond in the organic product is a disulfide bond.

on on on I A r3 l\ O+%m ss l-ms If the reaction is terminated whenone-fourth of the sulfur appears as hydrogen sulfide, the average sulfurbond will be a trisulfide. Similarily one-fifth of the charged sulfur ashydrogen sulfide corresponds to a tetrathiobisphenol. Theserelationships are valid only when all of the charged sulfur has enteredreaction.

The reaction between a phenol and sulfur results in a phenol polysulfideproduct as illustrated by the following formula:

l-Oll E wherein A is independently selected from the group consisting ofB is independently selected from the group consisting and i3 R isindependently selected from the group consisting of: hydrogen; halogen;hydroxy; nitro; alkyl or alkoxy of one to 20 carbon atoms; alkene of twoto 20 carbon atoms; aryloxy of six to 18 carbon atoms; cyclic alkyl ofthree to 20 carbon atoms; carboxyor carbalkoxy of two to 20 carbonatoms; carbaryloxy from seven to 18 carbon atoms;

and

L to 6', m is a number from 0 to about n =0 to 4; T =0 to 3; e=0 to 5;):is a number from 2 to about 7.

The novel polythiobisphenols or phenol polysulfides of this inventionproduced from a phenol and sulfur in the presence of a Friedel-Craftscatalyst have a special utility in that they are reducible tomercaptophenols. The phenolic rings are linked by a sulfur bondcontaining at least two sulfur atoms in order to be reducible tomercaptophenol. Thus, thiobisphenol can not be reduced tomercaptophenol. The phenol sulfides produced as described in BritishPat. No. 1,045,813 contain only minor amounts of disulfide and can beconverted only in negligible yields to mercaptophenol.

Mercaptophenols are useful compounds because they'have two functionalgroups attached to the aromatic ring. Metallic salts of orthomercaptophenol may be used as stabilizers for plastics such aspolyethylene or polyvinyl chloride. They render the plastic lessamenable to degradation by light and heat. In addition phospholanederivatives can also be used as polymer stabilizers.

Friedel-Crafts catalysts are described in Friedel- Crafts And RelatedReactions Edited by George A. Olah. Friedel-Crafts catalysts" aregenerally electron acceptors, falling into the general class of acids asdefined by G. N. Lewis. Further acidic catalysts of the Friedel-Craftstype can be divided into the following groups; (a) acidic halides (Lewisacids); (b) metal alkyls and alkoxides; (c) proton acids (Bronstedacids); (d) acidic oxides and sulfides (acidic chalcides); (2) cationexchange resins; (f) metathetic cation-forming agents and (g) stablecarbonium and related com- 5 SbCl FeCl TeCl SnCl TiCl TeCl BiCl and HF.

The preferred catalysts are para toluenesulfonic acid anhydrides ormonohydrate and BF with the latter the most preferred.

The phenols that can be used in this reaction include phenol;alkylphenols having one or more side chains up to about twenty carbonatoms, such as 2,4-dioctylphenol or dodecylphenol; chloro-orbromophenols, such as, 2-4,dichlorophenol; arylphenols such as 4-benzylphenol or 4-phenylphenol;

hydroxyphenols such as catechol, alkoxy-or aryloxyphenols such asmethoxy or phenoxyphenol; carboxyphenols such as salicyclic acid as wellas the corresponding esters, i.e., ethyl salicylate. Other suitablephenolic reagents are the naphthols and the bisphenols typified by4,4'-isopropy]idenediphenol.

The proportions of sulfur and phenol suitable to give phenol sulfidesrange from about 0.3 to about 3.0 gram moles of phenol per gram atom ofsulfur, preferably from about 0.3 to about 2.0. A second preferredproportion is from about 0.5 to 1.0 moles of phenol.

The quantity of Friedel-Crafts catalyst which is employed ranges fromabout 0.01 to about 0.5 mole per mole of phenolic compound, preferablyfrom about 0.05 to about 0.2 mole per mole of phenol. A second preferredquantity is about 0.1 mole per mole of phenol.

The temperature employed in conducting the phenol sulfide reactionranges from about C to about 250 C, preferably about 125 to about 200 C.and even more preferably about to about l75 C.

The reduction of the phenol polysulfides can be carried out by a numberof methods, such as those described in co-pending applications Ser. No.597,228, now abandoned, and Ser. No. 666,915, now U.S. Pat. No.3,468,961, issued Sept. 23, 1969. The preferred processes are, forexample, the action of metals and acid, catalytic hydrogenation orreduction employing alkali metal sulfides.

In the process of preparing o-mercaptophenol a byproduct of phenolmonosulfide is produced. Further during the distillation ofortho-mercaptophenol, additional phenol monosulfide is formed. Thesebyproducts of monosulfides can be converted by hydrogenolysis to phenol,a reactant, and hydrogen sultide as described in the following reactionformulas.

Hydrogenolysis may be effected by heating the phenol monosulfide at atemperature of about 150 C to about 250 C, under a hydrogen pressure ofabout 500 psi to about 3000 psi or higher in the presence of a suitablehydrogenation catalyst, such as those described above as useful in theinitial reduction step.

The following examples are to illustrate the invention; all temperaturesare in degrees centigrade.

EXAMPLE 1 Reaction of Phenol and Sulfur as Catalyzed by p-Toluenesulfonic Acid A stirred mixture of 2102 g. (22.5 moles) ofphenol, 480g. moles) of sulfur flowers and 37.5 g. (0.197 moles) ofp-toluene-sulfonic acid monohydrate was heated at 175 C for 14 hours.During this period 87.5g of hydrogen sulfide was evolved. This quantityrepresents 17.2 percent of the charged sulfur. The reaction was stoppedand phenol, 1695g. was then removed by stripping the reaction mixture toa temperature of 150 at 15mm. pressure.

The molecular weight, as determined by vapor-phase osmometry, of theresidue product was 343. The average ratio of sulfur atoms (elementaland chemically combined) to polysulfide bonds in the residue product, ascalculated from the quantity of hydrogen sulfide evolved, is 4.8.

EXAMPLE 2 In a manner similar to Example 1 a mixture of ten molequantities of phenol and sulfur was heated at 175 for ten hours in thepresence of g. (0.131 moles) of p-toluenesulfonic acid monohydrate,which effected the evolution of 60g. of hydrogen sulfide. The productremaining after filtering off 71g. of sulfur and after stripping 633g.of phenol had a molecular weight of 437 and a sulfur content of 43.8percent. These data correspond to the average structure:

OH on on l I l 1 lv lo. 134

EXAMPLE 3 Conversion of a Phenol Polysulfide Mixture to Mercaptophenol A500g. portion of the residue product of Example 1, (corresponds to 2.79moles of phenol) and 33g. of cobalt sulfide catalyst was stirred andheated at 125 under 1300-2200 pounds per square inch of hydrogenpressure for 15 hours, i.e., until the hydrogen pressure no longer fell.After filtering off the catalyst, the hydrogenated product wasdistilled. The composition of the distillate was demonstrated by gaschromatographic separation and analysis of a trimethylsilylated portionof the distillate. It contained 83.9g. of o-mercaptophenol, ll.lg. ofp-mercaptophenol, 1.2g. of a material which the gas chromatographicelution time indicated to be m-mercaptophenol, and 83.8g. of phenol.These quantities represent yields of 38.6 percent of o-mercaptophenoland 5.1 percent of p-mercaptophenol. The gas chromatographic analysiswas validated by a similar analysis of authentic samples ofmercaptophenol.

EXAMPLE 4 Reaction of Phenol and Sulfur as Catalyzed by BoronTrifluoride A stirred solution of 14l0g. (15 moles) of phenol, 480g. (15moles) of sulfur flowers and 7.05g. (0.104 mole) of boron trifluoridewas heated at 150 until 88g. of hydrogen sulfide was evolved which isequivalent to 17 percent of the charged sulfur. This required 2.5 hours.The reaction mixture deposited 91g. of sulfur (which was removed byfiltration) during a storage period of several days. The filtrate wasstripped of phenol, 911g, by distillation at 14 mm. of pressure to atemperature of 180, leaving a residue of 792g. containing 37.3 percentsulfur. The average ratio of sulfur atoms to polysulfide bond of theresidue, a phenol polysulfide, is 3.7.

EXAMPLE 5 Conversion of Phenol Polysulfide Mixture of Mercaptophenol A500g. portion of the residue of Example 4, which corresponds to 3.35moles of phenol, was reduced by hydrogenation as described in Example 3.The product was separated into fractions by distillation through a 16inch vigreux column. The fractions and their compositions as shown bygas chromatographic analysis are listed below:

FRACTIONAL DISTILLATION OF REDUCED POLYTHIOBISPHOLS (at 15 mm pressure)Weight of Components (g) Vapor Temperature Phenol Mercaptophenol OrthoPara Totals: 57 93 Yield 27 24 EXAMPLE 6 Conversion of PhenolMonosulfide to Phenol A phenol-sulfur condensation product was preparedby heating a solution of 7520g of phenol (80 moles) l280g of sulfurflowers (40 moles) and 9.0g of sodium hydroxide at l80l for 20 hours.

Unchanged phenol was stripped off under reduced pressure. The residueremained contained 15.7 percent sulfur and had a molecular weight of248. These analyses indicate the following average structure:

A mixture of 500g of this product and 339 of cobalt sulfide catalyst washeated at 200 under 2500 pounds/sq. in. of hydrogen. Hydrogen uptakeoccurred. After the pressure had fallen to about 800 pounds, theautoclave was vented to release hydrogen sulfide and then pressurizedwith hydrogen back to 2500 pounds. This procedure was repeated fourtimes. The reaction mixture was filtered to remove catalyst and thendistilled at 19 mm. Phenol, 331 g, was collected at 77-95. Thiscorresponds to a yield of 77.5 percent.

EXAMPLE 7 Conversion of Phenol Monosulfide to Phenol A composite ofresidues from several hydrogenation runs, 520 gms, containing 99.5g ofsulfur was heated at 200 in the same manner as in the above example. Thephenol obtained, 343g, corresponded to 80.5 percent yield.

As can be seen from the above examples phenol polysulfides and phenolmonosulfides are produced from the reaction of sulfur and a phenol.These products are reduced to mercaptophenol and a residue containingphenol monosulfides. These phenol monosulfides are then converted byhydrogenolysis to a phenol which is recycled to the first stage whereina phenol is reacted with sulfur.

What is claimed is:

l. A process for the production of mercaptophenols comprising reactingat a temperature from about 125 to about 250 centigrade sulfur with aphenol selected from the group consisting of wherein R is independentlyselected from the group consisting of hydrogen, chlorine, bromine,hydroxy,

alkyl of one to 20 carbon atoms, alkene of two to 20 carbon atoms,methoxy, phenoxy,

wherein A is independently selected from the group consisting of Ru andJ1 B is independently selected from the group consisting of and R isindependently selected from the group consisting of hydrogen, chlorine,bromine, hydroxy, mcthoxy, alkyl of one to 20 carbon atoms, alkene oftwo to 20 carbon atoms, phenoxy,

Ulla

L is 0 to 6; m is a number from 0 to about 5; n is 0 to 4; e is 0 to 5',T is from 0 to 3; .r is a number 2 to about 7; and the mercaptophenolsare a mixture of ortho and para mercaptophenols.

3. The process of claim 2 wherein the reaction is interrupted at anytime up until approximately one forth of the charged sulfur has evolvedas hydrogen sulfide.

4. The process of claim 2 wherein the reaction is interrupted at anytime up until approximately one fifth of the charged sulfur is evolvedas hydrogen sulfide.

5. The process of claim 2 wherein the reaction is operated from about toabout centigrade.

6. The process of claim 2 wherein the catalyst employed is borontrifluoride.

7. The process of claim 2 wherein the catalyst employed is para toluenesulfonic acid.

8. The process of claim 2 wherein the catalyst is employed in an amountof from about 0.5 to about 2.0 moles per mole of the phenol reactant.

9. The process of claim 7 wherein the mercaptophenols are a mixturecomprising about 80 percent ortho mercaptophenols and about 10 percentpara mercaptophenols.

wherein A is independently selected from the group consisting of B isindependently selected from the group consisting h and R isindependently selected from the group consisting of hydrogen, chlorine,bromine, hydroxy, alkyl of one to carbon atoms; alkene of two to 20carbon atoms; methoxy and phenoxy, and

L is 0 to 6; m is a number from O to about 5; n is from 0 to 4; e isfrom 0 to 5; T is from O to 3; x is a number from 2 to about 7;

2. reducing the phenol polysulfide to mercapto phenol and a phenolmonosulfide;

3. separating the mercapto phenol;

4. converting the phenol monosulfide to phenol; and

5. introducing the phenol from step 4 into step 1.

11. The process of claim 10 wherein steps (2) and (4) are performed bymeans of catalytic hydrogenatlon.

12. The process of claim 10 wherein the catalyst employed is borontrifluoride.

13. The process of claim 10 wherein the catalyst employed is paratoluene sulfonic acid.

14. The process of claim 10 wherein the reaction is operated at fromabout to about centigrade.

1. A process for the production of mercaptophenols comprising reactingat a temperature from about 125* to about 250* centigrade sulfur with aphenol selected from the group consisting of wherein R is independentlyselected from the group consisting of hydrogen, chlorine, bromine,hydroxy, alkyl of one to 20 carbon atoms, alkene of two to 20 carbonatoms, methoxy, phenoxy, n is 0 to 4 and L is 0 to 6 in the presence ofa Friedel-Crafts catalyst, interrupting the reaction at any time upuntil approximately one third of the charged sulfur has evolved ashydrogen sulfide, Thereby producing a sulfur rich phenol polysulfidehaving at least two sulfur atoms per linkage connecting each pair ofhydroxy-substituted rings of said phenol polysulfide and reducing saidphenol polysulfide with a reducing agent to produce the correspondingmercaptophenol.
 2. The process of claim 1 wherein the phenol polysulfidehas the formula wherein A is independently selected from the groupconsisting of B is independently selected from the group consisting of Ris independently selected from the group consisting of hydrogen,chlorine, bromine, hydroxy, methoxy, alkyl of one to 20 carbon atoms,alkene of two to 20 carbon atoms, phenoxy, L is 0 to 6; m is a numberfrom 0 to about 5; n is 0 to 4; e is 0 to 5; T is from 0 to 3; x is anumber 2 to about 7; and the mercaptophenols are a mixture of ortho andpara mercaptophenols.
 2. reducing the phenol polysulfide to mercaptophenol and a phenol monosulfide;
 3. separating the mercapto phenol; 3.The process of claim 2 wherein the reaction is interrupted at any timeup until approximately one forth of the charged sulfur has evolved ashydrogen sulfide.
 4. The process of claim 2 wherein the reaction isinterrupted at any time up until approximately one fifth of the chargedsulfur is evolved as hydrogen sulfide.
 4. converting the phenolmonosulfide to phenol; and
 5. introducing the phenol from step 4 intostep
 1. 5. The process of claim 2 wherein the reaction is operated fromabout 150* to about 175* centigrade.
 6. The process of claim 2 whereinthe catalyst employed is boron trifluoride.
 7. The process of claim 2wherein the catalyst employed is para toluene sulfonic acid.
 8. Theprocess of claim 2 wherein the catalyst is employed in an amount of fromabout 0.5 to about 2.0 moles per mole of the phenol reactant.
 9. Theprocess of claim 7 wherein the mercaptophenols are a mixture comprisingabout 80 percent ortho mercaptophenols and about 10 percent paramercaptophenols.
 10. A process for continuously producing amercaptophenol comprising (1) reacting at a temperature from about 125*centigrade to about 250* centigrade a phenol and sulfur in the presenceof a Friedel-Crafts catalyst selected from the group consisting of paratoluene sulfonic acid and boron trifluoride, interrupting the reactionany time up until approximately one third of the charged sulfur hasevolved as hydrogen sulfide and producing a compound of the formulawherein A is independently selected from the group consisting of B isindependently selected from the group consisting of R is independentlyselected from the group consisting of hydrogen, chlorine, bromine,hydroxy, alkyl of one to 20 carbon atoms; alkene of two to 20 carbonatoms; methoxy and phenoxy, and L is 0 to 6; m is a number from 0 toabout 5; n is from 0 to 4; e is from 0 to 5; T is from 0 to 3; x is anumber from 2 to about 7;
 11. The process of claim 10 wherein steps (2)and (4) are performed by means of catalytic hydrogenation.
 12. Theprocess of claim 10 wherein the catalyst employed is boron trifluoride.13. The process of claim 10 wherein the catalyst employed is paratoluene sulfonic acid.